Bring a large saucepan of water to a boil. Add carrots, and cook just until tender. Drain, and return the carrots to the pan. Set aside.

Heat oil in a skillet over medium heat. Sauté onion and garlic until soft, about 5 minutes. Transfer the onion and garlic to the saucepan with the carrots, and pour in chicken stock. Turn heat to medium-low, cover and simmer for 25 minutes to blend flavors.

Puree the carrot mixture in a food processor or blender, in small batches if necessary. Return to the saucepan, and stir in the milk, dill and chives.